Disposable absorbent articles, such as diapers, pull-on diapers, training pants, adult incontinence pads, wipes, facial tissue, toilet tissue, napkins, paper towels and the like are often manufactured and/or packaged on a high-speed production line where individual articles may move along a production path at a speed of hundreds of meters per minute. During the manufacturing and/or packaging process it is not uncommon for the disposable absorbent article to undergo a folding process. For example, a disposable diaper may undergo a bifolding process prior to being placed in a package. In a bifolding process, an article is folded into two parts. The article may be folded in half in the longitudinal direction such that two opposing portions of the article are brought together in a face-to-face configuration. At least some manufacturers of disposable diapers desire to provide a bifolded diaper that has a front end edge that is substantially aligned with a back end edge of the diaper. However, current manufacturing practices often do not provide the desired degree of alignment between the diaper end edges, resulting in a diaper that may have undesirable characteristics in the marketplace. The problem may be further compounded for so-called “training pant” diapers which, after being folded into a U in the same or similar way as conventional diapers, are joined permanently, e.g., sealed, along the lateral portions to form a closed annular girdle enabling the diaper to be used pant-fashion. The high degree of precision for folding training pants may require increased accuracy beyond that of a traditional diaper, so that the lateral portions of the training pant, which are to be joined permanently, are configured with the desired overlap.
In one method for providing a folded absorbent article, a portion of a production line for making absorbent articles may include a primary roll for carrying the absorbent article. The primary roll typically uses suction force, e.g. vacuum, to hold the absorbent article in the proper position during the folding process. The process may also include one or more secondary rolls for pulling a portion of the absorbent article, typically the leading end portion, off of the primary roll. The secondary roll(s) may employ vacuum pressure to pull the leading portion of the absorbent article off of the first roll and hold the pulled off portion to the secondary roll surface of the second roll. As the manufacturing process or converting operation continues, more of the leading end portion of the article may continue to be pulled off of the primary roll and attached to the secondary roll. Eventually, the article may be subjected to forces that pull the leading and trailing portions of the article in substantially opposite directions. In some instances, clips or other mechanical holding means may be used to hold the middle portion of the absorbent article to the surface of the primary roll in order to provide sufficient force to pull the leading end portion of the article off of the secondary roll. Typically, once the leading end portion of the article is pulled off of or released by the secondary roll, the leading end portion will travel back toward the primary roll to continue through the folding process. However, when the leading end portion of the article is pulled/released from the secondary roll, it may be subjected to turbulence or other forces that cause it to move about in an uncontrolled manner, potentially resulting in a folded article with undesirably misaligned end and/or side edges.
In order to overcome the problems associated with the uncontrolled movement of the leading end portion when it is separated from the secondary roll, some manufacturers may add a transfer roll or conveyor configured with a vacuum system to receive the leading end portion of the absorbent article and transfer it back to the primary roll. Typically, the surface of the transfer roll or conveyor includes a porous belt or other foraminous surface that allows the suction force of the vacuum system to be exerted at the surface of the conveyor or roll. The surface speed of the transfer conveyor or roll is typically constant, and in some instances is set to match the surface speed of the primary roll. In this way, the leading end portion of the article can be transferred back to the primary roll at about the same speed as the trailing end portion is travelling, potentially reducing the chance for misalignment of the leading and trailing end portions during folding. However, when the leading end portion of the article is separated from the secondary roll, the relative speeds of the leading end portion and the surface of the transfer conveyor or roll may still be substantially different. While the transfer roll or conveyor may be able to capture the leading end portion and hold it to the conveyor or roll surface with vacuum pressure and thereby minimize uncontrolled movement, the leading end portion may still end up in an undesirable configuration (e.g., wrikled, bunched, crooked, etc.) due to the rapid acceleration typically experienced by the leading edge when it contacts the transfer roll or conveyor.
In addition to the issues related to the different speeds of the transfer conveyor surface and the leading end portion of the article pointed out above, a transfer conveyor or roll may also reduce the speed and/or efficiency at which the manufacturing line can operate. In order to reduce the amount of time it takes to transfer the leading end portion from the peel roll to the transfer conveyor/roll it may be desirable to minimize the distance between the surface of the transfer conveyor/roll and the surface of the secondary roll. However, this typically results in clearances between these two components that only permit one article to be processed at a time. In other words, a second leading end portion cannot be transferred to the secondary roll until the first leading end portion is sufficiently clear of the secondary roll, or the progress of the second leading end portion may be impeded by the presence of the first leading end portion. Further, providing smaller clearances between the surfaces of the various rolls/conveyors may result in reduced manufacturing tolerances and robustness.
In another effort to address the problem of undesirably misaligned end edges, some manufacturers of absorbent articles may include additional material in the end edge portion of the absorbent article so that any misaligned edges can be cut off during the production process. The articles having the cut end edges may appear to be more aligned and still have an end edge of suitable length. But by providing additional material that must be cut off, material and manufacturing costs for producing the absorbent article may increase undesirably. Additionally, other portions of the article may still be noticeably misaligned.
Accordingly, it would be desirable to provide a system for folding articles and providing substantially aligned end and/or side edges on the folded articles. It would also be desirable to provide a system for making such articles without increasing the amount of raw material required to make the absorbent article. It would further be desirable to provide a system for making such articles at an increased manufacturing line speed.